Why March Brings the Most Variety of Extreme Weather in the U.S.

3/18/2019 (Permalink)

When March arrives, what are the first things you think of? Spring, baseball, flowers blooming?

The atmosphere in March is often much less tranquil. Based on history, one could make an argument that March consistently sees the greatest variety of dangerous weather of any month in the U.S.

By definition, spring is a transition time between the persistent cold of winter and the heat of summer. The sun is increasingly higher in the sky each day, and there's increasing daylight, allowing the air to warm more efficiently.

At the same time, there's still lingering snowpack and colder air in Canada and parts of the northern and western U.S. in March.

Superimposed on this tension between increasing warmth and lingering cold is a still-active March jet stream, often taking large southward plunges over the U.S.

When this happens, the potential energy of the temperature contrast gets released in the form of an intensifying low-pressure system that can spawn a snowstorm, severe weather outbreak, rainfall flooding, coastal flooding and high winds. 

It began with a squall line of severe thunderstorms racing across the eastern Gulf of Mexico, driving storm surge over much of Florida's Gulf Coast. That squall line then raced across the Florida Peninsula, spawning 11 tornadoes. Wind gusts up to 109 mph were clocked in the Dry Tortugas, west of Key West. Havana, Cuba, suffered a blackout due to the high winds.

(MORE: Historic Coastal Floods in the East)

To the north, whiteout conditions were reported in Atlanta, 6-foot drifts were seen near Birmingham, Alabama, and double-digit snowfall fell in 20 states from Alabama to Maine. Thousands were isolated by snow in the Southeast, and over 200 hikers needed to be rescued in the Smoky Mountains.

For the first time in history, every major airport on the East Coast was closed for a period of time due to this storm.

While not every March storm is a "Superstorm", the history of March storms is a long one. Here are some highlights by impact.

Snowstorms

Multiple parts of the county have seen their share of powerhouse March snowstorms.

(MORE: Where March is the Snowiest Month)

These snowstorms often either hook out of the Rockies into the Plains, or track up the East Coast.

Denver's second heaviest snowstorm was a mid-March 2003 whopper, when over 2.5 feet of snow in less than two-days' time effectively shut down the city.

(MORE: 4 Dangers of Heavy, Wet Snow)

Just four days after spring officially arrived, over 6 inches of snow buried a swath from Atlanta to Charlotte to Raleigh in 1983. 

The deadliest March snowstorm was the infamous Blizzard of 1888, which dumped 40 to 60 inches of snow in New York, Connecticut and New Jersey, wind-whipped into drifts which topped some homes. Four hundred were killed in the storm and its cold aftermath.

Here are a sampling of other notable March snowstorms:

• Late March 1987: Three-day blizzard produced gusts to 78 mph at Dodge City, Kansas and Altus, Oklahoma. Pampa, Texas, picked up 20 inches of snow. Forty-six Kansas counties declared disaster areas.
• Early March 1966: Blizzard across North Dakota, Minnesota produced wind gusts to 100 mph, whipping snow into drifts 30 to 40 feet high, paralyzing travel for three days. 
• Early March 1717: Four separate snowstorms hit the East in nine days, with up to 4 feet of snow in Boston and drifts to 25 feet in Dorchester, Massachusetts. 

Tornado Outbreaks

While severe weather can occur any time of year the ingredients align, March is typically when arctic fronts become less potent enough to allow warm, humid air to surge north more often in their wake ahead of vigorous jet-stream disturbances swinging out of the West.

The tornado threat tends to be highest in March in a corridor from the Southern Plains into the Tennessee Valley and Deep South. Central Florida can also be a tornado hot spot in March. 

(MORE: Tornadoes in March)

Occasionally, these outbreaks occur farther north, when unusually warm and humid air intrudes ahead of a powerful jet stream and frontal system.

On March 29, 1998, 14 tornadoes, 13 of which were spawned from one supercell, tore through southern Minnesota, including the towns of Comfrey and St. Peter.

Even in what most conventionally think of as "tornado alley", the March 13, 1990, outbreak was a massive outbreak for March.

Fifty-nine tornadoes were spawned in Oklahoma, Kansas, Nebraska and Iowa, including a pair of F5s in Hesston and Goessel, Kansas. These were the strongest tornadoes reported so far northwest in the U.S. so early in the season.

Perhaps the most infamous March outbreak was the Tri-State Tornado Outbreak in 1925, claiming 747 lives in seven states on March 18, 1925.

According to Dr. Greg Forbes, severe weather expert for The Weather Channel, recent research has found that instead of being one single tornado, it's now believed a family of at least three tornadoes had a combined path of at least 235 miles in Missouri, Illinois and Indiana.

Here are some other notable severe weather and tornado events in March:

• March 28, 2000: Back-to-back tornadoes struck Ft. Worth, then Arlington, Texas, shattering windows, killing three.
• March 25, 1992: Hail up to 4 inches in diameter pelted the Orlando metro area, virtually shutting down the area's nursery industry due to broken glass.
• March 28, 1984: At least 22 tornadoes tore through the Carolinas, including a 2.5-mile wide F4 near Tatum, South Carolina
• March 25, 1952: Deadliest outbreak in Arkansas history, with 111 dead. In all, tornadoes claimed 343 lives in the South. One F4 tornado leveled the town of Judsonia, Arkansas.
• March 20-22, 1932: One of the worst outbreaks in U.S. history from Mississippi to South Carolina to Indiana. Ten F4 tornadoes tore through Alabama, Georgia and Tennessee on March 21 alone.

Floods

Snow melting quickly during a sharp warm spell can and often does trigger spring flooding.

Some of the most serious flooding occurs when heavy rain falls in the spring as the ground is still soaked from absorbing spring meltwater. 

The early March 1997 flood was the highest in Cincinnati since 1964, and in some places in 60 years. Parts of the Ohio Valley picked up 10 to 13 inches of rain, sending the Ohio River and its tributaries into major flood. 

During the heart of the Dust Bowl, a mid-March "great flood" in 1936 set records in Pittsburgh, with additional flooding stretching as far northeast as Maine. 

(MORE: Flood Disasters More Common Inland)

Another destructive "great flood" in March 1913 was estimated to have claimed at least 1,000 lives, swamping the Miami River Valley of Ohio, including Dayton. 

Most recently, over 21 inches of rain triggered record flooding in parts of east Texas, Louisiana and Mississippi in March 2016. Particularly hard hit were the cities of Monroe and Shreveport, Louisiana, as well as the Sabine River.

East, West Coast Storms

We earlier mentioned the 1993 Superstorm as perhaps the ultimate, recent example of March's fury.

Certainly there are other examples of fierce nor'easters in March, including a late March 1984 storm that produced nearly 100 mph winds at Martha's Vineyard, and the infamously destructive Ash Wednesday 1962 storm along the Mid-Atlantic seaboard. 

Some March storms in the West can pack heavy snow, high winds and flooding rain.

In that same storm siege, over 11 inches of rain fell in the mountains above Santa Barbara, California, and winds gusted to 110 mph in Big Bear, California. 

By early March 1983, snow depths at Lake Tahoe reached 215 inches, prompting officials to warn cross-country skiers to avoid skiing into power lines buried by the massive snowpack.

Up to 18 inches of rain fell in parts of the L.A. Basin during that storm parade, punctuated by a pair of tornadoes on March 1, 1983.

An 8-foot wall of water roared down Santa Ana Canyon on March 3, 1938, after torrential rain, swamping areas between Santa Ana and Huntington Beach. Nineteen were killed and 2,000 were left homeless by this flood. 

Another 113 lives were lost in flooding along the Los Angeles River from that 1938 event. 

Jon Erdman weather.com